The present invention relates to an electro-mechanical brake in which a brake pad is driven by a motor to generate a braking force.
JP-A-2004-92812 discloses an example of an electro-mechanical brake for automobile in which a motor other than a hydraulic means drives a brake pad to generate a braking force. In this example, a disk brake system of floating type in which a disk rotor is clamped between brake pads of a pair by the motor, a ball-screw mechanism for converting a rotation of the motor to a linear movement and a linearly movable part of the ball-screw mechanism. In this electro-mechanical brake, a piston position (pad contact position) at which the brake pads contact the disk rotor is detected, a piston is moved with respect to the pad contact position to adjust a clearance (pad clearance) between the brake pad and the disk rotor and control a pad pressing force. Therefore, in such electro-mechanical brake, an accuracy in determining the pad contact position affects an accuracy in adjusting the pad clearance and an accuracy in controlling the pad pressing force. According to the technique disclosed by the publication, in the disk brake, a pressing force sensor and an elastic member are arranged on a piston, a value of the pad pressing force at a timing at which brake pads contact the disk rotor is experimentally predetermined by moving the piston to increase the pad pressing force, and a position of the piston at which an actual pad pressing force becomes slightly greater than the above mentioned value during an operation for actually detecting the pad contact position is determined as the pad contact position to improve the accuracy in detecting the pad contact position.